Question

помогите доказать тождество : sin 200° + sin 20°=0

Answer 1

sin(x)+sin(y) = 2·sin(½(x+y))·cos(½(x-y)) 

  sin 200° + sin 20°=2·sin(½(220°))·cos(½(180°))  =2·sin110°cos90° =

= 2·sin110°*0=0